Field
This invention relates to an automotive wheel aligner of the machine vision type.
Background
Conventional camera-based 3D machine vision-type aligners are not very portable. Camera based wheel aligners have a pair of cameras mounted such that each camera can look down a side of the vehicle at targets attached to the wheels. The cameras are usually mounted about 100″ apart and are about 100″ in front of the vehicle. Also, the vehicle needs to be raised so the alignment technician can work underneath it. Thus, the aligner cameras either have to move up and down with the rack, or be mounted high enough to be able to see the targets when the rack is raised. The cameras can be over 100″ off the ground when raised. Conventional aligners also include a console that may house a monitor, printer, computer, and target and clamp storage. Many camera based aligners' cameras are bolted to the ground and cannot be moved from one alignment bay to the next. However, it is useful to be able to move the aligner to another bay, because the vehicle under test might require parts, and removing it from the rack is not feasible. In such a case, the aligner is no longer useable. It is therefore highly desirable to be able to move it to a new location.
There are some camera based aligners that are movable; however, these have some significant limitations. In one of these aligners, the camera beam is simply bolted to the side or back of the console. This makes for a very large assembly that needs to be rolled together through the shop. This assembly is over a 100″ wide, 36″ deep and at least 80″ high. There is no easy way to maneuver this aligner in what typically is a crowded shop environment. Another portable camera based aligner has separate poles for the cameras and the console, so the technician has to move three discrete components to the new location. Also, the cameras are mounted on poles that are over 100″ tall, and they are difficult to move through doors or other areas with a low ceiling. There are also other types of camera aligners that mount to the rack. These are smaller since there is no pole; however, there are special mounting requirements for each rack. It is clear that a better solution to the portable camera based aligner is desirable.
Machine vision vehicle alignment systems using movable cameras and targets attached to vehicle wheels, also known as “image aligners,” are well known. The targets are viewed by the cameras such that image data obtained for a prescribed alignment process can be used to calculate vehicle alignment angles for display through a user interface, usually a computer monitor. Early system implementations included rigid beams that connected the cameras so that their position and orientation with respect to each other could be determined and be relied upon as unchanging. Later system implementations were introduced comprising the use of cameras not rigidly connected to each other, but using a separate camera/target system to continuously calibrate the position of one vehicle mounted target viewing camera to another. This type of system is described in U.S. Pat. Nos. 5,535,522; 6,931,340; 6,959,253; and 6,968,282, all of which are hereby incorporated by reference herein in their entirety. An example of a vehicle wheel aligner using such image processing is the Visualiner 3D or “V3D”, commercially available from John Bean Company, Conway, Ark., a division of Snap-on Incorporated
There are many factors that influence the measurement of a vehicle that can lead to a good aligner and a good mechanic to get bad readings. An uneven roll surface during the roll back procedure can cause the wheel to move or rotate about a different axis than the one it is rolling about. Camera based aligners require measurements of alignment parameters, which include an axis of rotation, a wheel angle, a vehicle wheel plane, or a vehicle wheel center. Another influence in bad readings is if, during caster swing, the vehicle brakes are not locked and the vehicle rolls, or the skid plates and turntables are not unlocked or are sticky, then large forces can build up within the vehicle and cause a bad reading. Also, if during adjustment the skid plates or turn tables are sticky, there is a buildup of forces within the vehicle that adversely affect the alignment. Other areas of contribution to reduced accuracy is if the rack is twisted, or the vehicle is jacked up and not let down and settled correctly.
There is a need for an aligner to incorporate cameras that can take measurements fast enough and continuously to measure, detect, and correct or warn of a problem with the alignment measurement. Further, there is a need for an aligner that measures, detects or corrects all possible issues that might make the alignment readings incorrect. With such an aligner the technician can be confident that the alignment just performed is correct.
Current camera based aligners require a positioning or runout procedure to measure the wheel axis (also referred to as “wheel spindle” or “axis of rotation” throughout this document), and a steering swing procedure to measure the caster and steering axis inclination (SAI). This procedure is time consuming and frequently requires the technician to hold the vehicle steady at certain points of the positioning and caster swing.
There is a need for a faster positioning procedure and a faster caster swing procedure, where the mechanic can perform the procedure without stops or delays.
When an aligner is in need of repair, a service technician is sent to the site. Sometimes the issue could be solved if the service technician could operate the aligner remotely, avoiding a costly service call. Methods exist to take control of an aligner using special software and an internet connection, but there are limits to their capabilities.
There is a need for a remote display/interface for the technician on site using the equipment, and a remote display/interface that service personnel at a different location can use to control the aligner, all on a simple readily available device. A solution that easily does both of these in one simple architecture would be highly desirable.